Trapped air return system for fluid actuated fastener driving machines



United States Patent [72] Inventor Garry Perkins 3,363,517 91/416 chlcagotmmo's Primary Examiner Paul E. Maslousky 1968 Attorney-- 1. Walton Bader 45 Patented Au .11 1970 E 1 Assignee swigng|h;emc ABSTRACT: A fluid actuated fastener driving machine is Long Island City New York shown which is provided with a body having a drive chamber therewithin. A piston has a plurality of vertical laterally aCorp. of New York.

' spaced openings therewithin. A bumper IS provided with a number of openings and is impingeable with the piston at the completion of the drive stroke thereof. A return chamber is connected to the drive chamber through the openings within [54] 'ilsgAPPElilglk RETURN SYSTEM FOR FLUID the bumper 4 J FAS TEN ER DRIVING MACHINES A lower poppet control chamber and an upper poppet control alms6nrawmg Flgs' chamber are provided. An upwardly movable poppet valve has a' lower face disposed within the lower poppet control [52] U.StCl ...l/46l919/;/l865, chamber and an upper face disposed within the upper poppet [51] Int Cl F1 5 [17 control chamber. The lower face is a smaller operational area Folb 11/02 than the upper face. A first conduit is provided to conduct [50] Field Search 91,416 pressure air into the lower poppet control chamber and a 9l/469 second conduit is provided to conduct pressure air into the upper poppet control chamber. A trigger housing is connected to said second conduit. An exhaust conduit is connected with [56] References Cited the trigger housing. A trigger is disposed within the trigger housing which can selectively block either the second conduit UNlTED STATES PATENTS or the exhaust conduit. The poppet valve is provided with an $13,601 l/l894 Teal 91/416 opening which normally abuts the upper face of the piston. 2,983,922 5/1961 Juilts 92/85 Above the opening in the poppet is a seal which is normally 3,026,849 3/1962 Powers et al.. 91/469 spaced therefrom and a second exhaust conduit which is open 3,067,724 12/1962 Jenny et a1 9l/LAV to atmosphere. A spring normally biases the poppet into it 3,170,487 2/1965 Juilts et a1 91/LAV normal position.

I I 22 2s l/l968 Powers 45 as l Patented Aug. 11, 1970 3,523,489

Sheet 1 of 3 FIG.I

FIG.2

INVENTOR.

GARRY R. PERKINS BYj %M ATTORNEY Patented Aug. 11, 1970 I 3,523,4 9

Sheet 2 of 3 3s 36 34 37 29 4 A I v 33 4 Fl 6.3 4 v u ,8 .6

39 3| 1 39 I I 26 3s 22 I 25 i 27 42 l2 b 24 x /'!/!r "gm m A -B'1------\ g I JEQiLfl i 0 F l G 6 4 I 43 INVENTOR. 4 l 1 GARRY R. PERKINS 4o I i I BY ATTORNEY Patented Aug. 11, 1970 Sheet INVENTOR.

GARRY R. PERKINS ATTORNEY TRAPPED AIR RETURN SYSTEM FOR FLUID ACTUATED FASTENER DRIVING MACHINES DESCRIPTION OF THE INVENTION This invention relates to a fluid actuated fastener driving machine having a novel system for returning the piston to normal position.

Conventionally there are two (2) types of return systems utilized in fluid actuator fastener driving machines. These can be generally described as spring return systems or air return" systems. Air return systems are further divided into two (2) general types which are single spool" types and double spool" types. The air return system of this invention is a-single spool type.

The air return system of this invention can be further particularized as the trapped air type. In this type of return system a trapped air" chamber is provided which is designed to be filled with pressurized air on the down stroke" of the piston. When the piston reaches the completion of its drive stroke the air within the trapped air chamber is now pressurized and, when the pressurized air is removed from the driving portion of the piston, will return the piston to its normal position.

The air return system of this invention is further employed in connection with the novel poppet valve system which has been utilized by the assignee of this application in various other fastener driving devices of similar type.

Conventional trapped air systems for returning the piston have had a number of disadvantages. In conventional systems the trapped air chamber, upon the completion of the driving stroke of the piston, exerts a severe compressive force to return the piston to its normal position. As a result the piston is returned rather violently. If such a system is employed in connection with the type of poppet valve system utilized in this invention wherein the poppet valve normally lies adjacent the upper face of the piston the violent return will, in a relatively short time, damage the poppet valve andcause the machine to become inoperative. Furthermore, in conventional systems of this type, the air is introduced into the return chamber through an opening in the side of the piston. Therefore, of course, a seal must be provided to normally seal the opening. As the machine is operated during its service life the seal will eventually be destroyed and the machine will be rendered inoperative. In the device of this invention the openings are provided within the piston and are spaced from the sides thereof. Therefore there is no necessity for sealing these openings.

A further advantage of the construction of this invention lies in the fact that the parts are relatively simple and the number of seals required is relatively small. Hence there is very little friction of the piston during its travels making for greater efficiency and less wear upon the parts.

The above constitutes a brief description of this invention and some of the objects and advantages thereof. Other objects and advantages of this invention will become apparent to the reader of this specification as the description proceeds.

The invention will now be further described by reference to the accompanying drawings which are made a part of this specification.

FIG. I is a side elevational view ofa fastener driving device made in accordance with this invention.

FIG. 2 is a plan view of the device shown in FIG. 1.

FIG. 3 is a cross-sectional view of the device shown in FIG. 2 taken along lines 3-3 of FIG. 2. In this view the parts are shown in the normal rest position.

FIG. 4 is a side elevational view, partly in section, showing the position of the parts when the machine is operated and the piston has reached its extreme drive position.

FIG. 5 is a detail cross-sectional view taken along lines 5-5 of FIG. 4.

FIG. 6 is a fragmentary cross-sectional view taken along 'line's'6-6'ofFIG. 5. 1

Lil

The invention will now be further described by reference to the specific form thereof as shown in the accompanying drawings. In this connection, however, the reader is cautioned to note that the specific form of this invention as shown in the specification herein is merely for illustrative purposes and for purposes of example. Various changes and modifications could obviously be made within the spirit and scope of this invention.

The fastener driving machine 11 of this invention is formed with a housing 12 to which is attached a handle 13. A magazine 14 is adapted to hold a plurality of nails 15 which are sequentially driven into work. In order to feed the nails sequentially a feeding mechanism is employed but, in this invention, the feeding mechanism for the nails and the magazine thereof form no part. A feeding mechanism and magazine which could be operative in this invention are described in the the piston. While the relationship between the parts may be.

patent application now pending Serial No. 695,538 filed December 4, 1967. Other feeding mechanisms and magazine constructions could also be employed.

Within handle 13 is an air chamber 16 which is connected to a source of pressure air through a connector 17.

Chamber 16 is connected through conduit 18 to lower poppet -control chamber 19. Chamber 19 is pressurized throughout the operating cycle of the device.

Upper poppet control chamber 20 is also provided. Connected to upper poppet control 20 is conduit 21 which is joined to conduit 22 which in turn is joined to trigger housing 23. A trigger member 24 bears a spool portion 25 which is normally biased in down postion by coil spring 26.

Trigger housing 23 is open to atmosphere at 27 but such opening to atmosphere is normally blocked by spool 25.

A link 28 is employed to actuate trigger 24.

A poppet valve 29 is formed with a lower face 30 which normally abuts the upper face 31 of piston 32. Poppet 29 also bears an upper face 33.

Lower face 30 of poppet valve 29 has a smaller operational area. than upper face 33 thereof.

Poppet valve 29 is also provided with an opening 34. Opening 34 normally impinges conduit 35 which is open to atmosphere and is spaced from seal-36. A coil spring 37 is provided which normally biases poppet valve 29 into the position shown in FIG. 3.

A driver 38 depends downwardly from piston 32 and is utilized to selectively drive nails 15 into work.

Piston 32 is provided with a plurality of openings therewithin. Piston 32 is sealingly and reciprocatingly movable withindrive chamber 40. Piston 32 is sealed within drive chamber 40 by O-ring 41.

A return chamber 42 is also provided within housing 12. Return chamber 42 is provided with an opening 43 which in turn is connected to corresponding openings 44 within 7 bumper 45. Bumper 45 is impingea'ble with .piston 32 at the termination of the drive stroke of the piston'.

In the preferred modification of this invention, in order to obtain maximum efficiency, the volume of return chamber 42 should be the same as that of drive chamber 40. Also, it can be noted, the size of the openings 39 in the piston must bear some relationship to the operational area of the piston itself. Obviously if the openings are too small the device will not properly return since return chamber 42 will not be filled with pressure air. Conversely if the openings are too large the device will not properly operate since the pressure air, instead of driving the-- piston, will bleed through the openings into the return chamber and the piston will likewise not properly return because the pressure air will bleed out of the openings within varied there is acertain ratio which wfll not operate.

Preferably, in the preferred modification of this invention, the piston has a diameter of two and five eighth (2-5/8) inches and each of the holes within the piston have a diameter of three thirty-seconds (3/32) of an inch. I believe that if the total diameter of the openings within the piston are more than twenty-five (25%) percent of the operational area of the piston satisfactory operation will not be obtained. Furthermore if the total area of the openings within the piston is less than five (5%) percent of the total operational area of the piston I also believe that satisfactory operation will not be obtained.

The operation of this invention will now be explained.

Pressure air is caused to flow into the device through connector 17 into space 16 and chamber 19. Likewise because of the position of trigger 24 pressure air flows through conduit 22, conduit 21 and into chamber 20. At this point poppet valve 29 is biased downwardly through spring 37. While face 33 of poppet valve 29 has a greater operational area than face 30 thereof the difference in operational area is not sufficient to bias the valve in the down position without the intervention of spring 37.

In this position of the poppet the lower face 30 bears against piston 32 and therefore piston 32 is in its normal position. Furthermore opening 35 is connected to opening 34 of poppet 29 causing this structure to be open to atmosphere. When trigger 24 is depressed by the movement of link 28 spool 25 is moved into the position shown in FIG. 4. This causes conduit 22 to be open to atmosphere and pressure air can no longer flow into trigger housing 23 since spool 25 now blocks the entrance of pressure air therein. This causes exhaust ofchamber 20 to atmosphere. Such exhaust removes pressure from face 33 of poppet 29 and therefore the pressure within chamber 19 causes poppet 29 to rise as shown in FIG. 4 now sealing opening 34 against seal 36 and blocking communication between space 34 and conduit 35. Pressure air now flows from chamber 19 into drive chamber 40 and causes piston 32 to be moved downwardly thereby causing driver blade 38 to strike a nail l5 and drive it into work. At the same time pressure air flows through openings 39 in piston 32 thereby passing through openings 44 in bumper 45 through openings 43 and thereby filling chamber 42 with pressure air. This movement of pressure air also serves to cool bumper 45 and thereby increase its life.

.The final stage of this movement is shown in FIG. 4 where piston 32 now abuts bumper 45.

As pressure is released from trigger 24 spring 26 now biases trigger 24 into its normal position. At this point spool 25 blocks communication between trigger housing 23 and atmosphere but permits pressure air to flow into conduits 22 and 21. This causes space 20 to be pressurized and, since the operational area of face 33 of poppet 29 is greater than the operational area of face 30 poppet 29 now moves into the position shown in FIG. 3. At this stage opening 34 is spaced from seal 36 and communicates with opening 35 which is open to atmosphere. Pressure air then exhausts above piston 32 to atmosphere; However chamber 42 is now filled with pressure air. This pressure air now exerts an upward thrust on piston 32 thereby returning it to its normal position. The pressure air, as the piston is returned, also bleeds through openings 39 and exhausts to atmosphere through opening 34 in poppet 2'9 and opening 35 to atmosphere. Therefore, by the time piston 32 reaches the position shown in FIG. 3, the return is extremely gentle and poppet 29 is not damaged.

in the preferred modification of this invention element 38 is not sealingly connected to bumper 45 nor is it sealingly connected to the outer housing. There is a certain amount of air leakage around the lower portion of element 38. This is not sufficient to render the return system inoperative but will serve to remove any excess pressure air remaining after return of piston 32 to the normal position shown in FIG. 3.

The foregoing sets forth the manner in which the objects of this invention are achieved.

Iclaim:

I. A fluid actuated fastener driving machine comprising, in combination, a body, a drive chamber within said body, a piston within said body including an upper face portion, and a lower face portion, a downwardly depending driver blade secured to said piston, said piston also provided with a plurality of laterallyspaced o enings therethrough, said piston bein sidably, sealingly an reciprocatingly movable within sai drive chamber, a return chamber having the same fluid capacity as said drive chamber connected to said drive chamber through said openings within said piston, a first poppet control chamber, a second poppet control chamber, a poppet valve provided with an opening therewithin normally impinging against said piston, said poppet valve also having a first face within said first poppet control chamber and a second face within said second poppet control chamber, the first face of said poppet valve having a smaller operational area than said second face of said poppet valve and normally being sealingly connected in line with said piston so that pressure fluid does not normally abut the upper face portion of said piston, first means for conducting pressure fluid into said first poppet control chamber, second means for selectively conducting pressure fluid into said second poppet control chamber when said piston means are in normal rest position, third means for selectively exhausting pressure fluid from said second poppet control chamber. a trigger housing connected to said second means and to said third means, a trigger member within said trigger housing, said trigger selectively blocking either said second means or said third means, bumper means normally impingeable with said piston on the completion of the drive actuation thereof, said bumper means provided with an opening therein connected with the openings within said piston, the openings within said piston being of a size permitting pressure fluid to enter said return chamber upon the stroke drive of said piston and for said pressure fluid to be retained within said chamber, said openings being also of a size to permit said pressure fluid to actuate return of said piston on the return stroke thereof and thence to be exhausted from said chamber.

2. A fastener driving tool as described in Claim 1, the openings within said piston being substantially vertical and spaced from the sides thereof.

3. A fluid actuated fastener driving machine as described in Claim 1 including a seal normally spaced from said poppet but selectively engageable with said opening therewithin, and an exhaust conduit normally open but selectively blockable by said poppet.

4. A fluid actuated fastener driving machine as described in Claim 3 including spring means normally biasing said poppet into engaged position with the face of said piston. 

